NAD+ enhancer modulates macrophage phenotype into an anti-inflammatory character
LMT503, a novel NAD+ enhancer, was discovered by Lmito Therapeutics in an attempt to find IBD therapeutic candidates via modulation of macrophages (Figure 1a). NAD+ synthesis in macrophages has been reported to contribute to immune suppressive functions by increasing oxidative phosphorylation (Minhas et al., 2019). LMT503 works as an efficient substrate for NQO1 which can increase cellular NAD+/NADH ratio in BMDMs (Figure 1b). To investigate the effect of LMT503 on inflammatory macrophages, BMDMs were stimulated with LPS and then treated with LMT503. LMT503 treatment decreased levels of inflammatory signature molecules TNF-α and iNOS (Figure 1c) but increased anti-inflammatory signature molecules Arg1 and IL-10 (Figure 1d) in BMDMs. Sirtuins, a class III histone deacetylases dependent on NAD+, can inhibit NLRP3-inflammatory pathways of macrophages and favor anti-inflammatory polarization of macrophages (Pan, Dong, Huang, & Fang, 2022; S. Y. Park et al., 2017). LMT503 treated BMDMs showed increased expression of Sirtuins 1, 3, and 6 (Figure 4e). Upregulated expression of GATA3 is known to induce anti-inflammatory polarization of macrophages (Faas et al., 2021). Treatment with LMT503 increased the expression of GATA3 in BMDMs (Figure 1f). However, pro-inflammatory cytokine IL-1β level was decreased after LMT503 treatment (Figure 1g). Human monocytic THP-1 cells and human monocytes also showed increased levels of anti-inflammatory markers Arg1 and IL-10 (Figure 1h,i). These data suggest that LMT503 treatment could induce shift of pro-inflammatory macrophages to an anti-inflammatory character.